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Source of pure copper


#1

I am experiencing issues with my 14K and 18K yellow gold alloys cracking. I suspect it’s an issue with annealing/quenching/forging/rolling the alloy rather than alloy composition but because of the deep, mosaic like crack structure it could also be from impurities.

I used Rio grande’s copper wire. It was advertised as .999 pure copper or CDA110. This means the only other alloy “component” in the copper was 0.04% Oxygen. I thought this would be pure enough but maybe not? The gold and silver were both .9999 and .999 bullion.

For those who make their own alloys, what source of copper are you using. I have cracking problems whenever I alloy gold and am pulling my hair out over getting workable alloys. If I absolutely must I will purchase commercial alloys but would strongly (very strongly) prefer to make my own alloy and I know it’s possible if only I can get some goddamn good enough copper damn it!


#2

I used the same copper to alloy 14K green as well and no cracking. It had 5% copper. If that helps solve this mystery…


#3

Here is a picture of the wire to see the cracks.


#4

Hi. I don’t quench my ingots and I anneal only after about a 50% reduction in thickness. I have found that forging the ingot first seems to make the metal more malleable. The hammer blows penetrate the mass and break up the crystal structure.
I think that you are likely over-annealing although that may not be the problem. The alcohol quench is great—at “black” heat.

Good luck.

Andy


#5

Thanks. I should have said I only started annealing that often AFTER I tried working it like silver, that is a 3-4 annealed to reduce the 6 mm bar to 4 by 2 mm wire. That’s why I am so confused. Maybe it is impure. I found another source of copper and the analysis said it was 99.992% Cu, 0.0037% Fe, 0.0014% Sn. Maybe that could work?


#6

I personally think that alloying your own gold is penny wise and pound foolish.
Proprietary alloys for different Karat or
Color are formulated for specific reasons. Not being a metallurgist I leave that to the pros. A lot of alloys today are suitable for both casting and fabrication. There are some specifically for casting or fabrication.
Leave it to the pros and include the cost in your pricing.


#7

Penny wise and pound foolish to alloy? Uh, not necessarily. For example, if you are into working with 22k for fusing and granulation then you need to alloy your own gold because you’re going to need to make your own granules (different sizes) and match them to the back sheet. Also, for tubing, nobody makes it in 22k, so if you want it to match your other work, you need to alloy, roll the sheet, and make the tubes. Sure, you can buy different colors of gold in standard karats like 14, 18, etc., from different vendors, but at some point they’re not going to stock what you need in the size you need it in. The Brepohl book is a good resource for anyone who wants to do a deep dive into the subject: https://www.amazon.com/Theory-Practice-Goldsmithing-Erhard-Brepohl/dp/0961598492. It was translated from the German, so there are a few translation errors (or so I’ve been told) but otherwise it’s pretty solid.
–Makena


#8

I am not exactly wondering about whether or not it is financially smart to alloy my own gold, I do it to have control over colour among other things.

Here’s another question, will the impurities present in metals at the hundredth to thousandth of a percent level affect the properties of the gold alloy. For example, gold is often found in nature alloyed with lead. When refined to 999.9 parts per thousand pure, if there was some lead present at the 0.1 parts per thousand level would that cause problems? What about copper with iron impurities, iron certainly causes gold alloys to be brittle but if it was there in the few thousandths of a percent level it really shouldn’t be a problem, right?

Metals are seldom refined more than 999 parts per thousand or 999.9 parts per thousand but would the contaminants present at the 1 part per thousand to 0.1 parts per thousand level cause problems?


#9

Perhaps problem “the 1 part per thousand to 0.1 parts per thousand level cause problems?”. is an incorrect description. It is obvious that for many of us it isn’t even thought of at those levels. So maybe a more accurate perspective is that it may affect certain characteristics. Some of which may be undesirable at times.
Regards RLW


#10

Keep in mind that for hundreds of years the metals used in jewelry alloys were nowhere near 999 % pure. That should answer your question.